In Fukushima, earthquake survivors and rescue workers observe a moment of silence to mark the week since the temblor and tsunami. The death toll tops 7,000, surpassing that of the 1995 Kobe quake.

Momoko Onodera prays at an evacuation center as she talks about her husband,… (Paula Bronstein / Getty…)

Reporting from Tokyo and Morioka, Japan — Fighting exhaustion and radiation fears, engineers struggled anew Saturday to complete the crucial task of hooking a crippled nuclear plant to the electricity grid to help cool down damaged reactors. The official count of dead and missing in the quake and tsunami soared above 18,000, making this Japan's worst disaster since World War II.

In the earthquake zone, tears trickled down the cheeks of some survivors and rescue workers who observed a solemn moment of silence at 2:46 p.m. Friday, marking a week since the magnitude 9 temblor slammed Japan's northeastern coast.

The quake set off a chain of events culminating in the nuclear accident now ranked at 5 on a 7-point international scale. Still unknown is whether restoring power to the damaged reactors will significantly aid cooling efforts. The full extent of damage to cooling pumps from hydrogen explosions and corrosion from seawater that has been pumped in has not been assessed.

In what many considered an inevitable, and perhaps tardy, move, Japan's nuclear regulatory agency Friday upgraded the severity of the still-unfolding disaster at Fukushima, 150 miles north of Tokyo, from 4 to 5 on the international nuclear and radiological event scale, meaning it is "an accident with wider consequences." The 1979 Three Mile Island incident, previously considered the second-worst accident in recent decades, was rated a 5 — and it did not cause injuries or a significant release of radiation. The Chernobyl nuclear accident was a 7 — "a major accident" as defined by the scale.

In the earthquake and tsunami zone, hundreds of thousands of people remained displaced. Although the government pledged to accelerate relief efforts, hardship from hunger and cold remained rife. In the quake-shattered city of Miyako, City Hall official Tatsuyuki Kumagai said many of the sheltering survivors were suffering from deep anxiety that frayed customary Japanese fortitude.

"Some cry, others say they're sick of the food. Or they really want to take a bath," he said. The stress, he said, "comes out in different ways."

Establishing a final toll will probably take weeks, but the National Police Agency said the official death count had reached 7,197, surpassing that of the 1995 Kobe earthquake, and the number of those unaccounted for stood at 10,905. Recovery crews have yet to comb through enormous piles of tsunami-deposited debris in some remote areas.

As of Saturday, about 300 workers were operating inside the 12-mile evacuation zone surrounding the battered nuclear plant. A few dozen were in the complex itself, government and utility officials said. A nuclear safety official said their main objective was to attach power lines to two of the worst-hit reactors.

Other last-ditch measures were under discussion, however, including the drastic option of entombing the complex in cement to stave off a large-scale leak of radiation.

Emergency workers sprayed water toward the reactors for about an hour after midnight, said Kenji Kawasaki, an official from Japan's Nuclear and Industrial Safety Agency, and more dousing could occur later Saturday. Workers also managed to restart a diesel-powered backup pump that would be used for cooling reactors No. 5 and 6, the public broadcaster NHK said.

Both the government and the plant's operator, the Tokyo Electric Power Co., are on the defensive amid rising public anger over what many regard as an incomplete picture of events at the nuclear complex, coupled with what has been seen as a feeble relief effort.

In a possible sign of growing sensitivity to public criticism, the Health Ministry announced that it would ask the army for help in moving hospital patients who were trapped inside the 12-mile evacuation zone surrounding the Fukushima Daiichi plant. That word came shortly after NHK aired a segment portraying harrowing conditions at a hospital in the city of Minanisoma, part of which falls within the evacuation zone.

Seeking to deflect accusations of secrecy, Prime Minister Naoto Kan said Friday that the government has told the public everything it knows about the accident at the plant. "[Chief Cabinet Secretary Yukio] Edano and I have been disclosing all of the information that we had," he said.

Earlier, Kan pledged in a meeting with the head of the International Atomic Energy Agency, Yukiya Amano, to disclose as much information as possible about the unfolding nuclear crisis.

"The situation at the nuclear plant remains unpredictable," Kan said in the nationally broadcast news conference. "We will definitely overcome this crisis. I want people of this country to feel safe again."

Amano has described the situation as "very grave and serious" but pointed out that, until now, an uncontrolled release of large amounts of radiation had been avoided and that there was little danger to public health outside the evacuation zone.